So we got ahold of the cross tabs (pdf) in that KIRO-7 mayoral poll, and one particular set of numbers stand out. While challenger Ed Murray only leads incumbent Mike McGinn by a 33 to 29 percent margin overall, Murray's support is considerably stronger—41 to 29—among the 64 percent of respondents who say they will "definitely" vote. McGinn actually leads 28 to 22 among the 23 percent of respondents who say they will "probably" vote.
Two things to note from these numbers. First, when you adjust for various quirks, the KIRO-7 poll isn't really as much of an outlier as it at first appears, for they all show a double-digit lead for Murray among the most likely voters. Second, if McGinn is going to have a chance of pulling this one out, he's going to need to generate a lot more enthusiasm (and turnout!) from within his base.
To win this race, McGinn needs to both turn out his base and win the undecided vote. That's not impossible, but it isn't easy.